Synthesis and Surface Properties of Films Based on Solventless Liquid Fluorinated Oligoester

Abstract

Two kinds of solventless liquid oligoesters, linear and three-armed, were synthesized by direct esterification of a mixture of diacids and diol or triol. The molecular weights of such oligoesters are in the range 800−1000. Linear oligoesters have a single melting point of between −5 and 0 °C while only one glass transition temperature at about −60 °C was found for three-armed oligoesters. The oligoesters were partially end-capped with a perfluoroalkyl group by reacting with perfluoroalkyl acid chloride. A polymeric film was prepared from the homogeneous mixture of normal and fluorinated oligoesters and a liquid polyisocyanate cross-linker and cured at elevated temperatures. As the fluorine content in the films increases from 0 to about 1.4 wt %, the surface tension of the top surface decreases as much as 20 mN/m, indicating that the top surface is mainly occupied by low surface energy fluorine-containing species. The surface enrichment of fluorine-containing species is confirmed by X-ray photoelectron spe...